[issue28832] Reduce memset in dict creation

[INADA Naoki]

INADA Naoki added the comment:

$ ./python-default -m perf compare_to default.json patched.json  -G
Slower (2):
- xml_etree_iterparse: 328 ms +- 26 ms -> 350 ms +- 29 ms: 1.07x slower
- fannkuch: 1.58 sec +- 0.09 sec -> 1.65 sec +- 0.09 sec: 1.05x slower

Faster (9):
- scimark_sor: 870 ms +- 59 ms -> 800 ms +- 54 ms: 1.09x faster
- deltablue: 28.0 ms +- 2.1 ms -> 26.4 ms +- 1.6 ms: 1.06x faster
- regex_dna: 423 ms +- 26 ms -> 399 ms +- 26 ms: 1.06x faster
- scimark_sparse_mat_mult: 13.9 ms +- 1.0 ms -> 13.2 ms +- 0.9 ms: 1.06x faster
- raytrace: 2.16 sec +- 0.12 sec -> 2.07 sec +- 0.11 sec: 1.05x faster
- unpickle_pure_python: 1.36 ms +- 0.11 ms -> 1.31 ms +- 0.07 ms: 1.04x faster
- pickle_dict: 103 us +- 11 us -> 99.7 us +- 7.7 us: 1.03x faster
- scimark_monte_carlo: 408 ms +- 35 ms -> 397 ms +- 25 ms: 1.03x faster
- scimark_lu: 765 ms +- 49 ms -> 746 ms +- 55 ms: 1.03x faster

Benchmark hidden because not significant (53): 2to3, call_method, call_method_slots, call_method_unknown, call_simple, chameleon, chaos, crypto_pyaes, django_template, dulwich_log, float, genshi_text, gen
shi_xml, go, hexiom, html5lib, json_dumps, json_loads, logging_format, logging_silent, logging_simple, mako, meteor_contest, nbody, nqueens, pathlib, pickle, pickle_list, pickle_pure_python, pidigits, pyt
hon_startup, python_startup_no_site, regex_compile, regex_effbot, regex_v8, richards, scimark_fft, spectral_norm, sqlalchemy_declarative, sqlalchemy_imperative, sqlite_synth, sympy_expand, sympy_integrate
, sympy_str, sympy_sum, telco, tornado_http, unpack_sequence, unpickle, unpickle_list, xml_etree_generate, xml_etree_parse, xml_etree_process

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nosy: +haypo

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue28832>
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